1Department of Oral and Maxillofacial Surgery, School of Dentistry, Seoul National University, Seoul 110-749, Republic of Korea2Department of Oral Biochemistry, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 110-749, Republic of Korea3Department of Prosthodontics, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 110-749, Republic of Korea